Transparent Magnetic Glass-Ceramics

Transparent magnetic glass-ceramics were produced by infiltrating nano-porous glass with nitrate salts and firing. The resultant glass-ceramics contained spinel ferrite nanocrystals that exhibited ferromagnetic and supermagnetic behaviour depending on composition and firing temperature. Transparency in the near infrared was obtained when oxidising conditions were used to prevent Fe2+ formation, while the porous matrix ensured nano-sized crystallites to limit scattering losses. MnFe2O4 glass-ceramics treated at 1000 deg C offered the best combination of magnetic and optical properties with a saturation magnetization of 5.6 emu/g, a Verdet constant of 16.5 deg/cm, and losses below 3dB/mm at 1550nm.